Probably this 36" (914mm) f/6.3 large format "aerial reconnaissance" lens. When you google it Dallmeyer made some but this one is unbranded, I'm assuming it was probably military equipment. The actual lens is just the bottom section with the aperture adjustment lever sticking out about midway along it's length, the rest of it is just an adapter made from PVC pipe and a focussing helicoid salvaged from another lens.